Powering Pi B+ from usb hub

[Slategrey252]

Hi.

I'm trying to buy a powered USB hub that will enable me to power first 4, then 8 raspberry PI B+

The problem I am finding is that manufacturers are over rating their products. I've bought 2 different ones so far and neither has had the juice to run even 1 PI B+

Does any one have information or links to powered usb hubs that DO do what I want?

Any info/help would be appreciated

[RaTTuS]

if you want to attached USB peripherals look at 2A / RPi
for many RPi look at a proper PSU system

[joan]

It is worth pointing out that you can not back power the B+ (or A+?) through a USB hub. This was possible with earlier models. You would need to feed a B+ via the expansion header or via the microUSB socket.

[Slategrey252]

It is worth pointing out that you can not back power the B+ (or A+?) through a USB hub. This was possible with earlier models. You would need to feed a B+ via the expansion header or via the microUSB socket.

Yes. Perhaps I'm not being clear enough. My bad, sorry.

what I am trying to do is power up the raspberry from the powered usb hub through the micro usb power socket on the raspberry B+. I'm most definitely not back powering it.

I know it can be done, I've seen the videos however they fail to mention what powered usb hub they were using.

[RaTTuS]

most will work fine

[Slategrey252]

most will work fine

But apparently they don't because I have bought 2 powered usb hubs that don't provide enough power through each of their usb sockets, hence the reason I'm asking for specific powered usb hub makes/models/brands.

[RaTTuS]

post links to the ones you have that dont work .

you need >1A PSU for a RPI b+

check your micro USB lead - if is made from damp string
what is the power as measured from the test points

[davidcoton]

what is the power as measured from the test points

In the interests of pedantry, that should be voltage, not power. Power (Watts) is voltage (Volts) multiplied by current (Amps).

Poor power leads cause a loss of voltage, so measuring the voltage on the test pins of the Pi while it is running will reveal a problem with the lead or supply (that is, if the voltage is 4.75V or below). To eliminate the supply (hub, in this case) as the problem, measure the voltage at the hub output, again with the Pi running (this might be physically difficult). If the voltage here is still between 5V and 5.25V, then the lead is the problem. If the voltage here is also low, its a supply (hub) problem. It is also worth comparing readings with the Pi halted -- they will be higher, but it should be only a small increase. A big rise indicates a problem.